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Agreement Between iFR and Other Non-Hyperaemic Pressure Ratios in Severe Aortic Stenosis
Andrea Comella1, Jasmine Chan1, Harsh V Thakkar1
1Monash Cardiovascular Research Centre, Victorian Heart Institute, Monash University and Monash Health, Melbourne, Australia.
Insights
In severe aortic stenosis patients, other non-hyperemic pressure ratios (NHPR) accurately predict the instantaneous wave-free ratio (iFR). This confirms NHPR are reliable for assessing coronary artery disease significance in this population.
Area of Science:
- Cardiology
- Invasive Cardiovascular Physiology
- Interventional Cardiology
Background:
- The instantaneous wave-free ratio (iFR) is a validated tool for assessing the physiological significance of coronary artery disease (CAD).
- Previous research supports the interchangeability of various non-hyperemic pressure ratios (NHPR) in CAD assessment.
- The utility of NHPR, specifically iFR, in patients with severe aortic stenosis (AS) remains under-investigated.
Purpose of the Study:
- To evaluate the agreement and accuracy of alternative NHPR compared to iFR in patients with severe AS.
- To determine if NHPR can reliably assess the physiological significance of CAD in the context of severe AS.
Main Methods:
- A cohort of 42 patients with severe AS underwent invasive pressure-wire assessment.
- Data were collected to calculate iFR, resting Pd/Pa, diastolic pressure ratios (DPR, dPR), and Diastolic Hyperaemia-Free Ratio (DFR).
- Statistical analyses, including correlation and Receiver Operating Characteristic (ROC) analyses, were performed to compare iFR with other NHPR.
Main Results:
- A strong positive correlation was observed between iFR and all tested NHPR (Pd/Pa, DPR, dPR, DFR), with correlation coefficients (r) ranging from 0.91 to 0.99 (p < 0.001).
- ROC analyses demonstrated that all NHPR accurately identified an iFR threshold of ≤0.89, with areas under the curve (AUC) for Pd/Pa, DPR, dPR, and DFR being 0.965, 1.000, 0.974, and 0.989, respectively.
- While some NHPR showed numerical differences from iFR, their diagnostic accuracy for significant stenosis was high.
Conclusions:
- In patients with severe AS, all evaluated NHPR demonstrated high accuracy in predicting an iFR of <0.89.
- Clinicians can be reassured that utilizing alternative NHPR instead of iFR is a reasonable approach for assessing CAD physiological significance in severe AS.
- These findings support the broader applicability of NHPR in diverse patient populations with structural heart disease.
Background:
Instantaneous wave-free ratio (iFR) can reliably assess the physiological significance of coronary artery disease (CAD). Previous studies have demonstrated its interchangeability with other non-hyperaemic pressure ratios (NHPR), but there is no data exploring whether this association is maintained in patients with severe aortic stenosis (AS).
Methods:
Forty-two patients (67 lesions) with severe AS were recruited and underwent invasive pressure-wire assessment. Data were extracted to calculate iFR, resting Pd/Pa, diastolic pressure ratios (DPR and dPR), and Diastolic Hyperaemia-Free Ratio (DFR). iFR was then compared with other NHPR to determine agreement and accuracy.
Results:
Mean aortic gradient and dimensionless index were 44.3 ± 11.6 mmHg and 0.23 ± 0.04, respectively. Of the 67 vessels, 57% were LAD, 15% LCx, 13% RCA and 12% other. There was strong positive correlation between iFR and all other NHPR, including Pd/Pa (r = 0.91, p < 0.001), DPR (r = 0.99, p < 0.001), dPR (r = 0.97, p < 0.001) and DFR (r = 0.98, p < 0.001). While Bald-Altman analysis demonstrated that Pd/Pa and DFR were numerically different from iFR, ROC analyses demonstrated iFR ≤0.89 was accurately identified by all NHPRs; Pd/Pa (AUC = 0.965, 95% CI [0.928-0.994]), DPR (AUC = 1.000, 95% CI [1.000-1.000]), dPR (AUC = 0.974, 95% CI [0.937-1.000]), DFR (AUC = 0.989, 95% CI [0.968-1.000]).
Conclusion:
In patients with severe AS, all the included NHPR in this analysis accurately predicted iFR < 0.89. These data should reassure clinicians that use of alternative NHPR to iFR is reasonable when assessing the physiological significance of CAD in patients with severe AS.
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